Rotary drill bits are commonly used for drilling bore holes or wells in earth formations. One type of rotary drill bit is the fixed-cutter bit (often referred to as a “drag” bit), which typically includes a plurality of cutting elements secured to a face region of a bit body. The drill bit is attached to a drill string including tubular pipe and component segments coupled end-to-end between the drill bit and other drilling equipment at the surface. Equipment such as a rotary table or top drive may be used for rotating the drill string and the drill bit within the bore hole. Alternatively, the drill bit may be coupled to the drive shaft of a down-hole motor, which then may be used to rotate the drill bit, alone or in combination with rotation of the drill string from the surface.
In order to attach the drill bit to the drill string, the bit body of a conventional rotary drill bit typically is secured to a hardened steel shank having an American Petroleum Institute (API) thread connection for attaching the shank to the drill string. The bit body is typically secured to the shank by coupling the bit body and shank together and then securing the bit body to the shank. Many conventional drill bits comprise a bit body or bit crown having threads on a proximal connector portion. The threads are configured for aligning the longitudinal axis of the bit crown to the longitudinal axis of the shank. The shank and bit crown are then mechanically secured together. In some conventional drill bits, such as U.S. Publication No. 2007/0102198 to Oxford et al., the shank and bit body are mechanically secured together by welding the two pieces at a point of intersection to prevent detachment or unthreading during use.
For at least some materials used for conventional bit bodies, the use of a weld for affixing the bit body and the shank together may be detrimental to the material's performance. For example, a bit body may be formed from a material including a carbide material. Welding a carbide material to a steel shank commonly leads to a significantly weakened carbide base material, and may, in some cases, also weaken the material substantially so that cracks may form in the bit body through the heat affected zone of the carbide material.